Molding machine

ABSTRACT

A mold core includes a forming pin having a hollow interior and an end wall. A passage, preferably in the form of a hollow tube, extends into the hollow interior of the forming pin and has an end sealingly secured at a position spaced from the end wall of the forming pin. A poppet valve is disposed on the end wall of the forming pin. The poppet valve is responsive to air pressure within the passage to open and permit flow of air through the end wall of the forming pin to assist stripping of molded articles from the mold core. The poppet valve includes a valve element having an outer end at the end face of the forming pin and an inner end adjacent to the end of the passage. A spring preferably biases the valve element to a closed position. The spring preferably comprises a coil spring captured in compression between the valve element and the forming pin.

The present disclosure is directed to a machine for molding plasticarticles, such as closure shells or sealing liners within closureshells.

BACKGROUND AND SUMMARY OF THE DISCLOSURE

Machines for molding closure shells, or molding sealing liners withinclosure shells, typically include a turret or carousel that rotatesaround a vertical axis. A plurality of molds are provided around theperiphery of the carousel, in the form of male and female mold sectionsthat are aligned along vertical axes parallel to the axis of rotation.Cams drive one or both of the mold sections of each pair between an openposition, in which a molded part is stripped from the male mold sectionand a charge of plastic material is placed in the female mold section,and a closed position in which the male and female mold sections arebrought together to compression mold the shell or liner. In a linermachine, premade shells are placed in a nest when the mold sections areopen, and a charge or pellet of liner material is placed within theshell before the molds are closed. U.S. Patents that illustrate machinesof this type for compression molding plastic closure shells include U.S.Pat. Nos. 5,670,100, 5,989,007, 6,074,583 and 6,478,568. U.S. Patentsthat illustrate machines of this type for compression molding sealingliners within closure shells include U.S. Pat. No. 5,451,360.

Although vertical axis carousel-type machines of the noted type haveenjoyed substantial commercial acceptance and success, innovationremains desirable. In particular, in vertical axis carousel-typemachines, the mold forces and the weight of the rotating equipment areparallel to the vertical axis of rotation, creating a bending momentwith respect to the axis of rotation and the bearings and shaft thatsupport the carousel. Carousel-type machines also require a substantialamount of valuable floor space in a manufacturing facility. It is ageneral object of the present disclosure, in accordance with one aspectof the disclosure, to provide a method and apparatus for compressionmolding plastic articles, such as plastic closures and plastic linerswithin closure shells, which reduce the forces applied to the supportframe and bearings, reduce maintenance requirements and the amount ofenergy needed to operate the machine, and/or reduce the amount of floorspace required per machine.

The present disclosure involves a number of aspects that can beimplemented separately from or in combination with each other.

A mold core in accordance with one aspect of the present disclosure,which can be implemented for either compression and injection molding,includes a forming pin having a hollow interior and an end wall. Apassage, preferably in the form of a hollow tube, extends into thehollow interior of the forming pin and has an end sealingly secured at aposition spaced from the end wall of the forming pin. A poppet valve isdisposed on the end wall of the forming pin. The poppet valve isoperatively coupled to the forming pin and responsive to movement of theforming pin during operation to open the poppet valve and assiststripping of molded articles from the mold core. In the preferredembodiment, a spool valve feeds air under pressure through an airpassage to open the poppet valve. The poppet valve includes a valveelement having an outer end at the end face of the forming pin and aninner end adjacent to the end of the passage. A spring preferably biasesthe valve element to a closed position. The spring preferably comprisesa coil spring captured in compression between the valve element and theforming pin.

A mold cavity in accordance with another aspect of the disclosure, foreither compression or injection molding plastic articles, is adapted tobe secured in a pocket on a molding machine having coolant feed andreturn passages opening into the pocket. The mold cavity includes a moldcavity seat adapted to be received in the pocket and a mold cavityinsert secured within the seat. The seat and insert have opposedsurfaces that form first coolant passages between the seat and theinsert, and the seat has second coolant passages for connection to thefeed and return passages in the machine for circulating coolant from themachine through the mold cavity and back to the machine. The secondcoolant passages in the cavity seat preferably are such that the moldcavity, including both the seat and the insert, are adapted to berotated within the pocket selectively to open and close the first andsecond passages to coolant flow. The cavity preferably includes indiciafor registry with indicia on the cavity support to indicate whether thefirst and second passages are open or closed to coolant circulation.

In accordance with a further aspect of the present disclosure, which canbe implemented for either compression molding and injection molding, amold element, such as a mold core and/or a mold cavity, has at least twocomponents, at least one of which has at least one surface channel that,in assembly with another component, cooperates with an opposing surfaceof the other component to form a passage for circulating coolant betweenthe components. The components preferably are secured to each other bye-beam welding, which localizes the heating to the mating surfaces andallows the assembled components to cool rapidly and retain theirhardnesses. E-beam welding also reduces the likelihood of distortion ofthe mating components, and permits accurate control of the areas to bejoined. E-beam welding does not require use of a separate joiningmaterial, but rather heat-fuses the components to each other.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure, together with additional objects, features, advantagesand aspects thereof, will best be understood from the followingdescription, the appended claims and the accompanying drawings, inwhich:

FIG. 1 is a front elevational view of a compression molding machine inaccordance with one presently preferred embodiment of the disclosure;

FIG. 2 is a side elevational view of the compression molding machineillustrated in FIG. 1;

FIGS. 3A-3D together form a sectional view taken substantially along theline 3-3 in FIG. 2;

FIG. 4 is an enlarged view of a portion of FIGS. 3B-3C illustrating oneof the mold segment pairs;

FIGS. 5A and 5B together form a sectional view of a modification toFIGS. 3A-3D.

FIG. 6 is a fragmentary sectional view on an enlarged scale of amodification to the mold core in the embodiment of FIGS. 5A-5B;

FIG. 6A is an enlarged view of the portion of FIG. 6 within the area 6A;

FIGS. 6B-6E are sectional views of components in the mold core of FIG.6;

FIG. 7A is a fragmentary sectional view that illustrates the mold cavityin the embodiment of FIGS. 5A-5B; and

FIG. 7B is a fragmentary sectioned perspective view of the cavity andunderlying support in FIG. 7A.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The disclosure of U.S. application Ser. No. 11/109,374, filed Apr. 19,2005, is incorporated herein by reference.

FIGS. 1-2 illustrate a machine 20 for compression molding plasticclosure shells. Machine 20 includes a wheel 22 mounted on a shaft 24between spaced supports 26. Shaft 24 is coupled by a pulley 30 and abelt 32 to a motor for rotating shaft 24 and wheel 22 around ahorizontal axis. Wheel 22 includes a hub 37 (which may be part of shaft24) and a support 39 extending radially from hub 37. Support 39 maycomprise a disk or the like, or may be in the form of a plurality ofangularly spaced radially extending support spokes 38. Each supportspoke 38 is hollow at its outer end. A rod 40 is slidably supported bysleeve bearings 42 (FIGS. 3B-3C) within the hollow outer end of eachspoke 38. A crossbar 50 is coupled to the end of each rod 40, so thatthe combination of rod 40 and bar 50 is generally T-shaped as viewedfrom the tangential direction in FIG. 1. A pair of radially spacedexternal supports 44, 46 (FIGS. 3B-3C) are provided on each spoke 38. Aplurality of angularly spaced molds 52 are disposed around the peripheryof wheel 22, preferably on both sides of the wheel. Each mold 52 isdisposed between supports 44, 46 on an associated spoke 38 and an end ofcrossbar 50 on rod 40. All of the molds 52 preferably are identical.

Each mold 52 includes a radially inner first mold section or segment 54and a second mold section or segment 56 in radially outward alignmentwith an associated first mold segment 54 (FIGS. 3B-3C and 4). In theillustrated embodiments, the radially inner first mold segment 54 is amale mold segment, and the radially outer second mold segment 56 is afemale mold segment, although these mold segments could be reversed inaccordance with the broadest principles of the disclosure. First or malemold segment 54 includes a mold core 58 slidably mounted within asurrounding sleeve 60 (FIG. 4). Mold core 58 has an end or tip 62contoured for compression molding the inside surfaces of a closure shellin the embodiment of FIGS. 1-3D and 4 (and the embodiment of FIGS.5A-5B). A first or outer tube 64 extends coaxially through the hollowinterior of mold core 58 forming a first annular passage between theexterior surface of tube 64 and the interior surface of core 58. Asecond tube or other passage 66 extends through the interior of tube 64,preferably coaxially with tube 64 and core 58, forming a second annularpassage between the exterior surface of tube 66 and the interior surfaceof tube 64. The second annular passage between tubes 64, 66 is coupledat a manifold block 68 to a coolant inlet fitting 70. Likewise, thefirst annular passage between tube 64 and core 58 is coupled at manifoldblock 68 to a coolant outlet fitting 72. (The “inlet” and “outlet”functions can be reversed.) Thus, coolant can be fed from fitting 70through the second passage between tubes 64,66 to the tip 62 of core 58,and thence through the first passage between tube 64 and core 58 tooutlet fitting 72. An inlet 74 on manifold block 68 is coupled to theinterior of tube 66, and can be connected to a source of compressed airfor example to assist stripping of closure shells from core tip 62.Manifold block 68 preferably is mounted on the radially inner end ofmold core 58—i.e., the end opposite from core tip 62.

A stripper sleeve 76 (FIGS. 3B and 4) surrounds sleeve 60 and isslidably supported by a bearing 78 within support 46. A cap 80 issecured to support 46, and a coil spring 82 is captured in compressionbetween cap 80 and a washer 84 slidably disposed within support 46 inabutment with the inner end of stripper sleeve 76. Thus, spring 82biases stripper sleeve 76 toward the second or female mold segment 56 ofeach mold 52. When the mold is open, washer 84 abuts a surface 85 withinsupport 46 to limit outward movement of stripper sleeve 76 over core 58.A second coil spring 86 (FIGS. 3C and 4) is captured in compressionbetween manifold block 68 and an abutment 88 coupled to the end ofsleeve 60. Thus, core 58 is biased by spring 86 inwardly against sleeve60. Each support 44 (FIG. 3C) has an interior pocket 90 that opensradially outwardly toward and in alignment with the associated firstmold segment 54. A coil spring 92 is captured in compression within eachpocket 90 and engages an extension 94 coupled to an abutment 88 onsleeve 60. Thus, as pressure to form the closure shell or liner pusheson core 56, core 56 pushes against sleeve 60, which pushes againstspring 92 to maintain forming pressure on the melt. (Coil springs 92 canbe replaced by fluid springs.) Within pocket 90, spring 92 engages aplate 96 that is coupled to an adjustment screw 98 for individuallyadjusting the force applied by each spring 92.

Second or female mold segment 56 (FIGS. 3B and 4) preferably includes acavity-forming insert 100 having an extension 101 that receives a screw103 removably to mount the insert on a support block 102. Blocks 102 areremovably mounted on crossbar 50 by screws 105 (FIG. 3B). Block 102 hascoolant passages 106 that communicate in the illustrated embodiment withlateral passages 108,110 in crossbar 50, and thence to longitudinalradial passages 112,114 in rod 40. As best seen in FIG. 3D, passages112,114 in rod 40 are connected to fittings 116,118 for circulation ofcoolant through rod 40, crossbar 50 and block 102 to cool mold cavityinserts 100. It will be noted in FIG. 3D that fittings 116,118 extendthrough a slot 120 in spoke 38 to permit radial movement of rod 40 withrespect to spoke 38.

A cam follower roller 122 (FIGS. 1, 2, 3A) is rotatably mounted on a leg124 that extends radially outwardly from crossbar 50. (Directional wordssuch as “radially,” “laterally,” “outwardly,” “inwardly” and“tangentially” are employed by way of description and not limitationwith respect to the horizontal axis of rotation of the wheel.) Leg 124is offset from the axis of rod 40 on which crossbar 50 is mounted sothat cam follower roller 122 is aligned with the axis of rod 40. Eachcam follower roller 122 on each crossbar 50 thus is associated, in theillustrated exemplary embodiment, with two molds 52 located on oppositesides of wheel 22. A cam 126 preferably is disposed along the lower arcof the periphery of wheel 22, as best seen in FIG. 2, for engaging camfollower rollers 122 in sequence as wheel 22 rotates around itshorizontal axis. During counterclockwise rotation of wheel 22, in theorientation of FIG. 2, follower rollers 122 of each pair of molds 52 insequence are engaged and captured by cam 126 to pull second moldsegments 56 outwardly and downwardly away from first mold segments 54.When each mold in turn is fully open, molded parts or articles areremoved from the mold cavities by a suitable part removal mechanism 128(FIG. 1). A new mold charge is then placed within each mold cavity by asuitable charge placement apparatus 130. As wheel 22 continues rotation,second mold segments 56 in sequence are moved upwardly and inwardly totheir closed positions with respect to first mold segments 54 by thecounterclockwise end of cam 126, again in the orientation of FIG. 2.Molded article removal apparatus 128 and mold charge placement apparatus130 may be of any suitable types. For example, mold charge placementapparatus 130 may be a disk-type apparatus of the type illustrated inU.S. Pat. No. 5,603,964. As an alternative, exemplary mold chargeplacement devices 130 and molded part removal devices 128 may be asdisclosed in the above-referenced U.S. application. Hydraulic, pneumaticor electric actuators could be used on each spoke 38, instead of cam126, to move the second mold segment radially inwardly or outwardly.Referring to FIGS. 1, 3D, each spoke 38 preferably carries a latch 132for locking the mold sections to each other in the fully closed positionso that there is no need for cam 126 to extend entirely around theperiphery of wheel 22.

As the second or female mold segment is pulled away from the first ormale mold segment, downwardly in the embodiment illustrated in FIGS. 3Aand 4, this motion of the second or female mold segment strips themolded part from the first or male mold segment in this embodiment.Referring in particular to FIGS. 3A-3B, a collar 150 is seated in arecess 152 adjacent to the radially outer end of each stripper sleeve76. A pair of rods 154 extend from each collar 150 through associatedslide passages in crossbar 50 and carry associated abutment collars 156disposed radially outwardly of the crossbar. As second mold segment 56and crossbar 50 are pulled by cam 126 away from first mold segment 54,crossbar 50 approaches abutment collars 56. When crossbar 50 has beenpulled far enough away from first mold segment 54 to abut collars 156,further motion of crossbar 50 pulls stripper sleeve 76 along sleeve 60and core 58 toward the second mold segment so as to push or strip themolded closure shell from core tip 62. It will be noted in FIG. 3A inparticular that there preferably is lost motion between crossbar 50 andabutment collars 156 to ensure that second mold segment 56 has clearedcore tip 62 before moving stripper sleeve 76 to strip the part from thecore trip. Each spring 82 (FIGS. 3B and 4) biases the associatedstripper sleeve 76 toward second mold segment 56 so as to assiststripping of the molded closure shell. In this connection, as secondmold segment 56 is closed by cam 126, the open edge of cavity insert 100preferably engages the opposing end of stripper sleeve 76 and pushes thestripper sleeve against the force of coil spring 82. Abutment collars156 preferably are adjustably slidably positionable on rods 154 toadjust the amount of lost motion between crossbar 50 and stripper sleeve76 to a desired level. Crossbar 50, rods 154 and stripper sleeves 76prevent rotation of rod 40 within spoke 38. Cam 126 may comprise asingle solid cam structure, but preferably includes an over-pressurerelease as shown in FIG. 2.

FIGS. 5A-5B illustrate a modification to the male and female mold toolstack of FIGS. 3A-3B and 4. First or male mold segment 54 includes amold core 220 that will be described in detail in connection with FIGS.6-6E. Mold core 220 is surrounded by sleeve 60, which in turn issurrounded by stripper sleeve 76. Stripper sleeve 76 is mounted withinsupport 46 by a stripper sleeve body 369 and bearings 78. A cam roller370 is rotatably mounted on a shaft 372 that is secured to strippersleeve body 369 by screws 374. A stripping stop 376 surrounds shaft 372and is slidable in a slot 378 on support 46. During rotation of wheel 22(FIGS. 1-2), when the mold segments are open, cam roller 370 engages acam 380 adjacent to the wheel to move stripper sleeve radially outwardly(downwardly in FIGS. 5A-5B) to strip the molded closure shell off ofmold core 220. Thus, in this embodiment, the stripper sleeve isactivated by a separate cam 380 rather than by motion of second orfemale mold segment 56 as in the prior embodiment. Female mold segment56, including mold cavity 280, is described in connection with FIGS. 7Aand 7B. A spool valve 400 (FIG. 5B) is carried by manifold 68 and has anactuator pin 402 coupled to a stripper plate 404 through a springretainer 406 to feed air under pressure through tube 66 as strippersleeve 76 is actuated to assist stripping of the closure shell.

FIGS. 6-6E illustrate a mold core 220 (FIG. 5A) in accordance withanother aspect and embodiment of the disclosure. Elements in FIGS. 6A-6Ethat are identical or similar to elements previously discussed,particularly in connection with FIG. 5A, are indicated bycorrespondingly identical reference numerals. Mold core 220 includes aforming pin 222 (FIGS. 6 and 6E) having an end wall 224 contoured toform the molded component in question, such as the interior of a closureshell base wall or the interior surface of a sealing liner in accordancewith some preferred implementations of the disclosure. The end 225 ofcore forming pin 222 opposed to end wall 224 forms a hollow interior 226that preferably is concentric with forming pin sleeve 60 (FIGS. 6 and6B). The external surface of end 225 extends radially outwardly from thebody 227 of the forming pin, and a sleeve 228 (FIGS. 6 and 6D) extendsaxially from core pin end 225 surrounding body 227. Thus, there is afirst annular passage 230 between sleeve 228 and body 227 of forming pin222, and a second annular passage 232 between the radially outer surfaceof sleeve 228 and the inner surface of sleeve 60. The end of sleeve 228preferably is spaced from the interior surface of pin end wall 224, anda ring 234 (FIGS. 6 and 6C) is secured around the end of sleeve 228.Ring 234 preferably is disposed in an annular pocket within the end ofsleeve 60. Sleeve 228 can be connected to end 225 and ring 234 by anysuitable means, such as e-beam welding. The end of sleeve 60 has aninternal shoulder 244 against which forming pin end wall 224 is seated,and the sleeve and forming pin end wall are joined at 246 (FIG. 6A),preferably by e-beam welding. Shoulder 244 prevents burn-through duringwelding.

The mold stack embodiment of FIGS. 5A-5B is similar to that of FIGS.6-6E, except that the sleeve 228 is threaded at 442 to sleeve 60 in FIG.5A, so that there is no need for e-beam welding in FIGS. 5A-5B.

A plurality of radially extending fins or ribs 236 (FIGS. 6 and 6E)preferably are formed on the inner surface of pin end wall 224. Theseribs 236 extend from the outer surface of pin body 227 to a positionadjacent to but spaced from the outer periphery of end wall 224. Thelower surface (“lower” in the orientation of FIGS. 6 and 6C) of ring 234preferably abuts the upper surfaces of ribs 236, so that the channelsbetween the ribs form coolant passages between ring 234 and pin end wall224. A circumferential array of angularly spaced axially extending ribs238 (FIGS. 6 and 6B) on the inside surfaces of sleeve 60 preferably abutring 234 in assembly, so that the channels between the ribs form axialcoolant passages between ring 234 and sleeve 60. A circumferential arrayof angularly spaced radially extending ribs or fins 240 (FIGS. 6 and 6C)on the upper surface of ring 234 (in the orientation of FIGS. 6 and 6C)preferably abut an opposing internal shoulder 242 on sleeve 60 to formradial coolant passages between ring 234 and shoulder 242. Thus, coolantpreferably is circulated from within tube 64 to interior 226 of formingpin 222, through radially extending passages 248 in the forming pin intoannular passage 230, axially along annular passage 230, through theradially extending passages formed by ribs 236 between end wall 224 andring 234, axially through the channels formed by ribs 238 between ring234 and sleeve 60, radially inwardly through the channels formed by ribs240 between ring 234 and shoulder 242, and thence axially throughannular passage 232 to the coolant return. (The coolant flow directionless preferably can be reversed.) The cross-sectional area to coolantflow preferably is at a minimum in the axial channels formed by ribs 238between ring 234 and sleeve 60 to maximize the heat transfer in thisarea.

In accordance with another aspect of the present disclosure, forming pin222 may have a concentric axial passage 250 (FIGS. 6 and 6E) thatextends from interior 226 to the end face 252 of end wall 224. A poppetvalve 254 (FIG. 6) has an axially extending cylindrical body 256 thatextends through passage 250, and an enlarged conical head 258 adjacentto end face 252. A coil spring 260 preferably is captured in compressionbetween a retaining ring 262 on valve body 256 and an opposing axiallyfacing surface 264 on pin body 227 within interior 226. Thus, spring 260normally holds valve 254 in the closed position illustrated in FIG. 6.Air tube 66, which preferably is concentrically disposed within coolanttube 64, is coupled to a collar 266 disposed within hollow interior 226of core pin 222 between openings 248 and valve 254. A resilient sealingring 268 preferably is disposed within a channel 270 on collar 266 insealing engagement with the opposed interior surface of pin interior226. Collar 266 with sealing ring 268 cooperates with the hollowinterior of forming pin 222 to form a sealed air cavity 272 that isconnected to air tube 66. When tube 66 (or any other suitable passage)is supplied with air under pressure (e.g., by spool valve 400 in FIG.5B), poppet valve 254 moves outwardly against the force of spring 260.This bodily movement of the poppet valve not only itself assistsstripping of molded articles from end of core pin 220, but also feedsair under pressure through end wall 224 further to assist stripping ofthe molded articles. In this connection, it will be recognized thatpoppet body 256, 258 could be actuated mechanically, such as by a rod,rather than by air pressure.

FIGS. 7A and 7B illustrate a mold cavity 280 in accordance with yetanother aspect of the present disclosure. Mold cavity 280 preferably isdisposed in a pocket 282 on crossbar 50 (or other suitable mold supportstructure). Coolant feed and return passages 108,110 in crossbar 50 openat the axially facing bottom surface 284 of pocket 282. Mold cavity 280preferably includes a mold cavity insert 286 secured within a moldcavity seat 288, most preferably by clamp ring 302. Mold cavity seat 288preferably is cup-shaped, having an axially facing base 290 opposed tobottom surface 284 of pocket 282, and an annular rim 292 with a radiallyoutwardly facing surface opposed to the radially inwardly facing surfaceof pocket 282. Base 290 of seat 288 has a first opening 291 that opensto coolant passage 108 in bar 50. Opening 291 communicates throughpassage 296 and a central passage 293 to a cup-shaped space 295 betweenthe upper surface of seat 288 and the undersurface of insert 286. Thiscup-shaped space 295 communicates around the edge of seat 288 with anannular space 297 between the outer periphery of seat 288 and the innerperiphery of pocket 282. This space 297 connects through a passage 294with an opening 299 in base 290, and thence to coolant passage 110 inbar 50. Seat 288 extends at 101 for securement to crossbar 50 by screw103, as previously described. Cavity insert 286 preferably is generallycup-shaped, having a body 298 within rim 292 of seat 288, and a radiallyoutwardly extending lip or flange 300 that overlies the end of seat 288.Rim 300 is secured to crossbar 50 by a cavity retaining ring 302. Thus,coolant can circulate from passage 108 in crossbar 50 through opening291 and passage 296 in seat base 290, through passage 293 to space 295,through passages 297 and 294, and through opening 299 to passage 110 inbar 50. (Coolant flow could be in the reverse direction.)

In accordance with a preferred feature of this aspect of the disclosure,cavity insert 286 and seat 288 are rotatable conjointly and bodilywithin pocket 282 of crossbar 50 selectively to move cavity 280 betweenthe position illustrated in FIGS. 7A and 7B for permitting circulationof coolant, and an angularly spaced position for blocking circulation ofcoolant. A key 440 (FIG. 7A) couples cavity insert 286 to seat 288 sothat the insert and seat rotate together. For this purpose, indicia 312preferably are provided on insert rim 300 and retaining ring 302 toindicate whether mold cavity 280 is open or closed to coolantcirculation. Pockets 314 or the like preferably are provided in insertrim 300 for cooperation with a suitable tool to rotate the cavitybetween the open and closed positions for coolant circulation. Thus,ring 302 may be loosened and the cavity insert and seat rotatedconjointly so that openings 291, 299 in seat 288 no longer register withpassages 108, 110 in bar 50.

There thus have been disclosed a machine and method for compressionmolding plastic articles, which fully satisfy all of the objects andaims previously set forth. The disclosure has been presented inconjunction with several presently preferred embodiments, and a numberof additional modifications and variations have been discussed. Othermodifications and variations readily will suggest themselves to personsof ordinary skill in the art. The disclosure is intended to embrace allsuch modifications and variations as fall within the spirit and broadscope of the appended claims.

1. A machine for compression molding plastic articles, which includes: awheel mounted for rotation around an axis, a plurality of angularlyspaced molds, each including a first mold segment, and a second moldsegment, each of said second mold segments being movable with respect tothe associated first mold segment between a closed position with saidfirst mold segment and an open position spaced from the associated firstmold segment for removing a molded article from said mold and placing amold charge into said mold, one of said mold segments being a moldcavity including a mold cavity seat and a mold cavity insert within saidseat, said seat and said insert having opposed surfaces that form firstcoolant passages between said seat and said insert, said seat havingsecond coolant passages for connection to the coolant passages in saidwheel for circulating coolant from said wheel through said cavity andback to said wheel, wherein said second coolant passages in said seatare such that said mold cavity, including said seat and said insert, isadapted to be rotated selectively to open and close said first andsecond passages to circulation of coolant.
 2. The machine set forth inclaim 1 including indicia on said cavity for registry with indicia onsaid wheel to indicate whether said first and second passages are openor closed to coolant circulation.
 3. A mold cavity adapted to bereceived in a pocket on a molding machine having coolant feed and returnpassages opening into said pocket, said mold cavity including: a moldcavity seat adapted to be received in the pocket and a mold cavityinsert within said seat, said seat and said insert having opposedsurfaces that form first coolant passages between said seat and saidinsert, said seat having second coolant passages for connection to thefeed and return passages in the machine for circulating coolant from themachine through said cavity and back to the machine, wherein said secondcoolant passages in said seat are such that said mold cavity, includingsaid seat and said insert, is adapted to be rotated within the machinepocket selectively to open and close said first and second passages tocirculation of coolant from the support.
 4. The mold cavity set forth inclaim 3 including indicia on said cavity for registry with indicia onthe support to indicate whether said first and second passages are openor closed to coolant circulation.
 5. The mold cavity set forth in claim3 adapted to be received within a cup-shaped pocket in the machine inwhich the coolant flow and return passages open to a bottom surface ofthe cup-shaped pocket, wherein said seat has an undersurface withopenings for connecting said first and second passages to the openingsin the machine.